Most sprinkler control units incorporate a system for controlling a plurality of sprinkler stations for a selected time and a method of controlling such stations on predetermined days and designated times. These functions are usually carried out by a station timing dial, calendar dial and clock dial. Prior units also have provided dedicated stations to be controlled on a different cycle than nondedicated stations. For example, dedicated stations may be those which supply water to plants or shrubs which need more or less frequent watering than other stations.
The prior art sprinkler controllers include deficiencies in each of these areas of control. In most units, the components making up the individual station timing segments are so large that the number of segments must be limited, generally to six or seven stations. Even with limiting the number of station timing segments, the station dials are generally large. Where as many as ten or eleven station timing segments are provided, the dial size becomes excessive in its size.
In many prior art sprinkler controllers, the station timing dial turns at timing speed only and does not fast index subsequent to completion of its timing cycle. This does not permit skipping stations which are not connected or where the timing segment is set on "0" time. While many prior art units provide for manual operation, the provisions for such operation are in many cases only semiautomatic, while others use a series of separate switches which require additional expense and space requirements.
In most prior art units, the station timing dial provides for very inaccurate setting of the desired operation. In many cases, the force developed from actuated switches or sensors has a tendency to move the timing segment cam or lug out of position and thus change the desired setting.
With respect to the calendar and clock dials used on prior art units, many units incorporate pins for designating desired operation times and dates. These often become loose or lost during use. In some units, screws are required or various cams or gears must be removed and repositioned to change the timing sequence of the controller. Of course, these arrangements require tools and are inconvenient and time consuming to the user. Those prior art devices which require captive pins require additional wasted space in front of the dials to avoid interference with the housing cover or door. In some cases, the force developed from operating switches or sensors has a tendency to move the pin or cam out of position. Further, pins and cams often cannot readily be adapted to more than two positions and thus their incorporation into a design prevents alternate programming or requires more dial components to accomplish alternate or dual programming.
Where such pins or cams are used, the dials required are generally large in diameter or thick in depth. Both of these features result in additional wasted space.
In prior art units which attempt to provide a dual programming function, that is, where certain stations may be operated on a different schedule than others, such units have required that stations be dedicated to an alternate program. This limits the number of stations which can be used for a regular program of watering. In other units, separate switch groups are incorporated to accomplish multiple programming. These introduce additional expense and space requirements. In other prior art units, additional dials are incorporated to accomplish a multiple programming feature. Such arrangements greatly add to production costs and require additional space.